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Introduction to Washington State C-1

Department of Ecology's Requirements

for Rain Gardens in Western Washington

This appendix is divided into three sections:

• Background - An overview of the Washington State Department of Ecology’s requirements including implementation timelines
• Six Important Questions about Rain Gardens and the 2012 Stormwater Management Manual for Western Washington (SWMMWW) Minimum
Requirements - How rain gardens may be used to meet Ecology’s stormwater requirements

• References – A table of references and links to further resources.

Please note that local jurisdictions may have requirements that vary from Ecology’s stormwater requirements. You should talk with your municipal
building permits or development services department about your project to find out the exact requirements that apply to your project.

Background

The federal Clean Water Act requires cities and counties meeting certain population levels to have a National Pollutant Discharge Elimination System
(NPDES) permit for stormwater management. In Washington State, the Washington State Department of Ecology (Ecology) has been delegated
the authority to administer the NPDES permits. State law (RCW 90.48.030 and RCW 90.48.162) also authorizes Ecology to control impacts of
stormwater discharges to all waters of Washington State, including groundwater, through permits.

Requirements within the permits vary substantially between Western Washington and Eastern Washington. This appendix only discusses requirements
associated with Western Washington.

Ecology has issued two Municipal Stormwater General Permits to cities and counties within Western Washington based on population. The Phase
I Municipal Stormwater permit covers the Cities of Seattle and Tacoma, and Snohomish, Pierce, King and Clark Counties. The Phase II Western
Washington Municipal Stormwater permit covers approximately 82 cities and 5 counties in Western Washington. To see if your city or county is
covered under a Municipal Stormwater Permit visit http://www.ecy.wa.gov/programs/wq/stormwater/municipal/MuniStrmWtrPermList.html.

HOW DO THE MUNICIPAL STORMWATER PERMITS RELATE TO THE STORMWATER MANAGEMENT MANUAL FOR WESTERN
WASHINGTON (SWMMWW)?
Within the municipal stormwater permits, there are certain requirements associated with controlling stormwater runoff from new development,
redevelopment, and construction sites. As part of these requirements, cities and counties are required by their permit to adopt Minimum Requirements
that are the same as, or equivalent to, the minimum requirements within the Stormwater Management Manual for Western Washington (SWMMWW).